1. Field of the Invention
The present invention relates to a kneading extruder, which is suitably applicable to a plasticization kneading extruder for plastic material.
2. Description of the Related Art
One example of a plasticization kneading extruder for plastic material of related art is shown in FIG. 14. Twin screws 2 are provided in a cylinder 1 capable of heating and cooling. The screws 2 are coupled with a decelerator 4 and driven in the same rotating direction by a motor 3 coupled to the decelerator 4. The twin screws 2 are engaged with each other. The cylinder 1 has a feed port 5, a first vent 6a and a discharge port 7, which are placed in the order from the upstream of the cylinder 1. The screws 2 are configured by a solid transporting portion 8, a plasticization kneading portion 9 (a first kneading portion) and a molten material transporting portion 10 in the order from the upstream.
FIGS. 15A and 15B show another example of a plasticization kneading extruder for plastic material of related art.
In this case, twin screws 2 are provided in a cylinder 1 capable of heating and cooling. The screws 2 are coupled with a decelerator 4 and driven in the same rotating direction by a motor 3 coupled to the decelerator 4. The twin screws 2 are engaged with each other. The cylinder 1 has a feed port 5, first vent 6a, a side feeder 11, a second vent 6b and a discharge port 7, which are placed in the order from the upstream of the cylinder. The screws 2 are configured by a solid transporting portion 8, a plasticization kneading portion 9 (a first kneading portion), a first molten material transporting portion 10a, a molten kneading dispersion portion 12 (a second kneading portion) and a second molten material transporting portion 10b. A side feeder 13 is placed in the side feeder 11. The side feeder 13 is configured by a side feeder cylinder 14, a side feeder screw 15, a side feeder motor 16 and a side feeder decelerator 17. Two of the side feeder screws 15 are provided in the side feeder cylinder 14 to be able to generate the cooling. The side feeder screws 15 are coupled with the side feeder decelerator 17 and driven in the same rotating direction by the side feeder motor 16 coupled to the side feeder decelerator 17. The twin side feeder screws 15 are engaged with each other. The side feeder cylinder 14 has a side feeder port 18 from which solid sub-material (plastic, organic filler, inorganic filler, glass fiber, etc.) are supplied.
FIGS. 16A to 16C show typical disk type kneading wing disks configuring the plasticization kneading portion (the first kneading portion) 9 in FIG. 14, and the molten kneading dispersion portion (the second kneading portion) 12 in FIGS. 15A and 15B.
FIG. 16A shows a feeding wing (forward kneading: FK) functioning as forward kneading disks. FIG. 16B shows a return wing (backward kneading: BK) functioning as backward kneading disks. FIG. 16C shows a neutral wing (cross kneading: CK) functioning as cross kneading disks. With reference to each of the drawings, the left side is a side view of the wing, and the right side is a cross section view of the wing indicated by the arrows A-A on the left side view.
The FK is a kneading wing configured by five pieces of disks B, each of which is arranged at a phase angle E so that they are shifted in a position from one another in a flow direction of a plastic material H. The width of disk B is 0.1 to 0.9 times the diameter with respect to a cylinder inner wall F. Portions formed by flight vertexes of the disks B with respect to the cylinder inner wall F are tip portions G.
The BK is a kneading wing configured by five pieces of disks B, each of which is arranged at a phase angle E so that they are shifted in a position from one another in the backward direction opposite to the flow direction of the plastic material H. The width of disk B is 0.1 to 0.9 times the diameter with respect to a cylinder inner wall F. Portions formed by the flight vertexes of the disks B with respect to the cylinder inner wall F are tip portions G.
The CK is a kneading wing configured by five pieces of disks B, each of which is arranged at a phase angle E so that they are shifted at 90 degrees in a position from one another. The width of disk B is 0.1 to 0.9 times the diameter with respect to a cylinder inner wall F. Portions formed by flight vertexes of the disks B with respect to the cylinder inner wall F are tip portions G.
For the other types of kneading wings, there is a backward flight, a seal ring, a rotor and a kneading wing that flight tips are slanted at a helix angle θ to a screw shaft direction, as disclosed in JP-A-2005-35212.
Next, an operation will be described below.
In FIG. 14, a solid plastic material supplied from the feed port 5 is transported to the plasticization kneading portion 9 by the screws 2. The plasticization kneading portion 9 is configured by fitting together with the FK, BK and CK as shown in FIGS. 16A to 16C. The plasticization kneading portion 9 melts and kneads the solid plastic material within a short period of time. The molten plastic material at the plasticization kneading portion 9 is transported to the discharge port 7 while unnecessary volatile ingredients contained in the plastic material are removed through the first vent 6a of the molten material transporting portion 10. The molten plastic material is then discharged to an outside from the cylinder 1, with the material stranded in a shape from the discharge port 7. The molten plastic material discharged with the stranded shape is cut to pieces by a cutter (not shown) to form a pellet form. The cutter is placed directly on an exit of the discharge port 7 or on a position away from the exit. Unnecessary solid impurities contained in the molten plastic material may also be filtered by a screen 19 installed at front of the discharge port 7.
In FIGS. 15A and 15B, the solid plastic material supplied from the feed port 5 is transported to the plasticizing kneading portion 9 by the screws 2. The plasticization kneading portion 9 is configured by fitting together with the FK, BK and CK as shown in FIGS. 16A to 16C. The plasticization kneading portion 9 melts and kneads the solid plastic material within a short period of time. The molten plastic material in the plasticization kneading portion 9 is transported to the second kneading portion 12 while unnecessary volatile ingredients contained in the plastic material are removed through the first vent 6a of the first molten material transporting portion 10a. The side feeder 11 is installed at the first molten material transporting portion 10a. The side feeder 11 supplies solid sub-material (plastic, organic filler, inorganic filler, glass fiber, etc.) to the molten plastic material. The molten plastic material and solid sub-material are kneaded by the second kneading portion 12. The second kneading portion 12 is similar to the first kneading portion 9, and configured by the FK, BK and CK as shown in FIGS. 16A to 16C. The second kneading portion 12 melts, kneads and disperses the molten plastic material and solid sub-material within a short period of time. The molten, kneaded and dispersed compound material is transported to the discharge port 7 while the unnecessary volatile ingredients contained in the plastic material are removed through the second vent 6b of the second molten material transporting portion 10b, and discharged to the outside from the cylinder 1, with the material stranded in a shape, through the discharge port 7. The molten plastic material discharged with the stranded shape is then cut to pieces by a cutter (not shown) to form a pellet form. The cutter is placed directly on an exit of the discharge port 7 or on a position away from the exit. Unnecessary solid impurities contained in the molten plastic material may also be filtered by a screen 19 installed at front of the discharge port 7.
The plasticization kneading extruder for plastic material of related art has the structure as described above, and carries out the kneading for plasticization of solid plastic material, the melting, kneading and dispersion of the molten plastic material and sub-material within a short period of time, and then discharges the material.
The plasticization kneading portion 9 is configured by fitting together with a feed wing, a return wing and a neutral wing, in which the feed wing FK has a performance to transport the plastic material to the downstream of cylinder, the return wing BK has a performance to return it to the upstream of cylinder, and the neutral wing has no performance of transporting the material. These wings can be conformed to the property of plastic material and a demanded quality for the plastic compound material to be obtained from the kneading. The plasticization kneading portion 9 has a function of pushing the solid plastic material into a narrow clearance of the kneading wings, the clearance being formed between the cylinder inner wall F and the kneading wings by rotating the screws 2, while the solid plastic material transported from the solid transporting portion 8 is blocked to certain extent by the fitted together with kneading wings. The plastic material is then transformed to a molten state from the solid by the shear stress or energy generated at the clearance.
The molten kneading dispersion portion 12 for dealing with the molten plastic material and sub-material has also a function similar to that of the plasticization kneading portion 9. Thus, melting, kneading and dispersion are carried out at the clearance formed between the cylinder inner wall F and the kneading wings.
In the case of the respective kneading wings of disk type of related art which has the plasticization kneading portion 9 and molten kneading dispersion portion 12, in consideration of a piece of disk, this single disk has no performance to transport the material to the forward or backward in the cylinder, so that the plastic material may flow with a dwelling state caused by a pressure difference. For this reason, a great amount of the plastic material is blocked at the narrow clearance formed between the cylinder inner wall F and kneading wings, particularly at the tip portion G. Moreover, a local large force (inner pressure) is generated because the plastic material is pushed into the narrow clearance of the kneading wings owing to the rotation of screws 2. Particularly, there has been a problem that the cylinder inner wall F and/or the tip portion G is abraded away because the tip portion G of one kneading wing paired with the other tip portion G where a pressure is generated at both the tip portions of kneading wing, is contacted with the cylinder inner wall F.
In the molten kneading dispersion portion 12, there has also been a problem that the filler is condensed or clumped together, and the dispersion state of the filler becomes worse because of the force (inner pressure) generated at the tip portion G by the cylinder inner wall F and the tip of the kneading wing.
The kneading wing having the performance of the forward or backward transportation include types of a backward flight and a rotor. The backward transportation flight is a screw type kneading wing coupled with a flight having a performance of the backward transportation. Thus, there is no clearance between the disks in the disk type kneading wings of related art. The blocking performance against the solid plastic material is therefore high, and a relatively high pressure is generated at the clearance formed between the cylinder inner wall F and the kneading wings, in comparison with the disk type kneading wings of related art.
The rotor type is a screw type kneading wing coupled with a flight having a performance of the forward or backward transportation. The forward transportation rotor has no clearance between the disks in the disk type kneading wings of related art and has high performance of the forward transportation. Thus, the plastic material cannot be blocked by a single unit of the kneading wing. Because of this, in the case where the forward transportation rotor is incorporated in the plasticization kneading portion 9, the forward transportation rotor must be fitted together with the kneading wings having the blocking function. In this way, the forward transportation rotor can provide the shear stress or energy to the plastic material in such a way that the plastic material is blocked by the kneading wings having the blocking function. However, a great amount of the plastic material is pushed into the tip portions because the flights are coupled one another. Thus, a local large force (inner pressure) is generated at the tip portions. The backward transportation rotor has no clearance between the disks in the disk type kneading wings of related art and has high performance for the backward transportation. Because of this, the backward transportation rotor has a similar function to the backward transportation flight and generates a relatively high pressure in comparison with the disk type kneading wing of related art.